Throttle constructions of this type include a flap disk operated by a shaft to function as a closure member. The exhaust gas duct is equipped with an opening which extends approximately radially into the exhaust duct for mounting the closure member and for holding a bearing element for the operating shaft.
German Patent Publication (DE) 2,947,819 A1 discloses a throttle flap construction in which the closure member comprising a flap disk and an operating shaft is insertable into an end portion of the exhaust gas duct. For this purpose the end of the duct must be accessible so that the flap construction can be inserted axially into the inner diameter of the duct. This requirement poses difficulties if an open duct end is not readily available. In that case, it is necessary to cut the duct crosswise for installing the known throttle flap construction. Further, it is necessary that the diameter of the flap disk of the closure member is smaller than the inner diameter of the exhaust gas duct at the point of installation. As a result of this requirement it has been found that a sealed installation of the throttle flap construction into the exhaust gas duct is difficult, if not impossible. Thus, a complete sealing of the exhaust gas duct is not assured. However, such complete sealing of the duct must be met in an exhaust duct for an exhaust gas turbo-charger that has a switch-off feature.
German Patent Publication (DE) 2,946,747 A1 discloses an embodiment in which the throttle flap construction is insertable into the exhaust duct from the side in a substantially radial direction through an opening in the duct which is closeable by a flange of the throttle construction.